Several experimental and theoretical studies have suggested that the formation of surface alloys or the deposition of strained transition metal (TM) monolayers (ML) on TM supports can be considered as a route for the designing of new catalysts. In this work, we report an extensive first-principles investigation based on density functional theory of the adsorption of TM (Rh, Pd, Ir, Pt) on the Cu(111) and Au(111) surfaces considering TM coverages ranging from 1 / 9 , 2 / 9 , up to 1 ML. Although there are clear differences in the atomic radii of the Cu, Rh, Pd, Ir, Pt, and Au atoms, at low TM coverages, both systems exhibit similar behavior, namely, the lowest energy adsorption site for a single TM adatom is not in the hollow sites on the surface, but in the lattice sites located in the topmost layer. For TM/Au(111), this trend follows adatom by adatom up to the limit in which all the substrate Au atoms are exposed to the vacuum region, with the underlying TM adatoms, and it is also valid for Rh/Cu(111). For Pd, Ir, and Pt on Cu(111), the same trend is observed up to 4 / 9 , 8 / 9 , and 6 / 9 TM coverages, and the adatoms are exposed to the vacuum region for higher coverages. For TM/Au(111), our analyses indicate a tensile strain built-in due to the mixture of adatoms with smaller radii with Au with a larger radius in the same first (topmost) surface layer, while a compressive strain can be seen for TM/Cu(111), in particular for Pd, Ir, and Pt at high coverages, which favors the location of the TM adatoms on Cu (111). Judging by the Pauling electronegativity scale, we would expect a different behavior for the substrate work function change upon TM adsorption on Cu(111) and Au(111). However, a similar behavior was obtained for the lowest energy configurations on both substrates. This is rationalized in terms of the electronegativity differences, geometrical effect of atomic smoothing, the insertion of the adatoms in the first (topmost) surface layer, and the exposed layer to the vacuum region.

We report the results of extensive computational investigation of the adsorption properties of water and ethanol on several Cu-, Pt-, and Au-based substrates, including the close-packed unreconstructed Cu(111), Pt(111), and Au(111) surfaces, defected metal substrates with on-surface low-coordinated sites generated by the intermixing of Pt-Cu and Pt-Au in the topmost surface layers and strained on-surface and sub-surface Pt-layers at Cu(111) and Au(111) substrates. The calculations are based on the density functional theory (DFT) within the van der Waals (vdW) correction. For all the substrates, we found that water and ethanol bind via the anionic O atom to the cationic one-fold coordinated on-top metal sites, which enhances the adsorbate-substrate Coulomb interactions. For water, both DFT and DFT + vdW calculations predict a flat geometry. For ethanol, the DFT and DFT + vdW results are in contrast, namely, DFT yields a perpendicular orientation of the C-C bond with respect to the surface, while we obtained a parallel orientation of the C-C bond using DFT + vdW, which maximizes the adsorption energies. Despite expected deviations due to the nature of the weak adsorbate-substrate interactions, we found that the adsorption energy of water and ethanol shows a linear dependence as a function of the position of the center of gravity of the occupied d-band, and hence, the magnitude of the adsorption energy increases as the d-band center position shifts towards the Fermi energy. Thus, it indicates hybridization between the O p- and metal d-states, which determines the magnitude of the adsorption energy of water and ethanol on clean, low-coordinated, and strained noble and transition-metal substrates.